The present invention relates to a stripping composition which can be used in particular in the construction field, especially for the stripping of external organic coatings, such as thick plastic coatings (TPC), exterior waterproof coatings and thin films, and in the yachting field, for the stripping of antifouling paints.
Exterior waterproof coatings, with a rubbery appearance, are impermeable to air, to oxygen and to water vapour and are based on acrylic or styrene-acrylic polymers.
In the construction field, most paint strippers are based on methylene chloride with methanol added. They can be thickened with cellulose compounds and can comprise an inorganic filler.
However, there is an increasing search to replace methylene chloride because of its very high volatility and very high noxiousness. Replacement products for the synergistic methylene chloride-methanol mixture exist but they are generally much more expensive and form at least 90% by weight of the composition of the formulation. The remaining 10% are composed of a thickener (generally chosen from cellulose or acrylic derivatives), itself generally even more expensive than the solvents, and various additives: activator, surfactant or corrosion inhibitor.
In the yachting field, the stripping of the antifouling coating, composed of numerous paint layers (5 to 10), is carried out by sanding down. This way of operating is lengthy and produces a great deal of dust. In addition, the use of stripping formulas based on methylene chloride is prohibited as they attack the gelcoat, which is a leaktight coating.
A subject-matter of the present invention is thus a stripping composition which can be used in particular in the construction field, especially for the stripping of exterior waterproof coatings, thick plastic coatings (TPC) and thin films, and in the yachting field, for the stripping of antifouling paints, characterized in that it comprises:
(A) at least one dibasic ester,
(B) at least one dipolar aprotic solvent,
(C) at least one inorganic filler with a thickening nature,
(D) water,
(E) at least one activator,
(F) at least one dispersant, and
(G) at least one cellulose thickener.
The composition according to the invention can comprise, per 100 parts by weight of (A)+(B)+(C)+(D)+(E)+(F)+(G):
10 to 50, in particular 25 to 45, parts by weight of (A);
10 to 30, in particular 15 to 25, parts by weight of (B);
20 to 40, in particular 25 to 35, parts by weight of (C);
10 to 25, in particular 15 to 20, parts by weight of (D);
1 to 15, in particular 1 to 10, parts by weight of (E);
0.2 to 2, in particular 0.4 to 1.2, parts by weight of (F); and
0.2 to 1, in particular 0.3 to 0.6, part by weight of (G).
The dibasic ester or esters (A) are chosen in particular from aliphatic dibasic esters, in particular C1-C4 alkyl diesters of one or more C4-C6 aliphatic dibasic acids. Mention may in particular be made of dimethyl succinate, dimethyl glutarate, dimethyl adipate and their mixtures.
The dipolar aprotic solvents (B) are advantageously chosen from dimethyl sulphoxide, N-methylpyrrolidone, propylene carbonate, dimethylformamide, acetonitrile, N-methylmorpholine, butyrolactone and dimethylacetamide. Dimethyl sulphoxide and N-methylpyrrolidone are preferred.
The term xe2x80x9cinorganic filler with a thickening nature (C)xe2x80x9d is understood to mean a natural or synthetic inorganic powder which can result in formulations for which the viscosity is of the order of 6 000 mPaxc2x7s at 20 revolutions/min or 2 000 mPaxc2x7s at 100 revolutions/min.
The inorganic filler or fillers generally have a mean particle size of between 0.1 and 200 xcexcm, more particularly between 1 and 100 xcexcm. A finer particle size makes it possible to obtain the same viscosity while using less filler, which is not economically desirable.
Mention may be made, as examples of inorganic fillers, of calcium carbonate, silica, calcium phosphite, calcium hydroxide (Ca(OH)2), clay or bentonite. Preferably, calcium phosphite will be used.
Mention will be made, as activators (E) which can be used according to the present invention, of alkyl alkoxypropionates, such as ethyl 3-ethoxypropionate (EEP), terpenes, such as D-limonene, or the mixture of these compounds.
Use will preferably be made of ethyl 3-ethoxypropionate and/or D-limonene.
Mention may be made, as example of dispersing agent (F), of the acidic phosphoric ester of 2-ethylhexanol, sold by Ceca under the name Beycostat A081.
Mention may be made, as example of cellulose thickener (G), of Methocell 311, sold by Dow Chemical Co., the process for the preparation of which is disclosed in U.S. Pat. No. 3,388,082, entitled xe2x80x9cHydroxypropyl methyl cellulose ethersxe2x80x9d.
The stripping composition of the invention has proved to be highly advantageous; this is because, after it has been applied and then left to act for a few tens of minutes, it is sufficient to shift the dry strips using a paint knife. Wet and sticky waste, which is always difficult to remove and to treat, is avoided and most of the time a clean substrate, such as a concrete or brick wall, is obtained.
In addition, in the yachting field, the stripping composition does not attack the gelcoat layer, which is a leaktight coating generally of polyester.
The stripping composition according to the present invention also exhibits the advantage of being stable on storage.